Since polypropylene has advantages of a low cost, a light weight, a high strength, a good chemical resistance, a good processing manufacturability, being easy to be recycled and the like, recently it is widely used in automobiles. However, a shortcoming of the polypropylene is that its low-temperature tenacity is poor. CN101659768 discloses a low-temperature impact resistant polypropylene composition, a preparation method and use thereof as automotive interior parts. The polypropylene composition comprises the following components in percentage by weight: 40-79.8% of a polypropylene resin, 15-35% of a mineral filler, 5-30% of a flexibilizer, 0.1-1% of an antioxidant, and 0.1-1% of a weather-proof agent. All kinds of properties of the automotive interior parts which are prepared from the polypropylene composition by an injection processing can meet an application requirement. The polypropylene composition overcomes a drawback of a poor low-temperature performance, and especially has a good low-temperature impact resistant performance at 0° C. to −40° C. CN101709122A discloses a polypropylene nanocomposite for automobile in a technical field of inorganic chemical industry, and a preparation method thereof. The preparation method comprises: controlling the degradation of a PP with the use of a twin-screw extruder under a temperature of 190-210° C. to ensure a MFR of the PP to be 15-30 g/10 min, then blending the PP with ball-milled inorganic powders, elastomers and a copolymerized PP to pellet with a twin-screw. The polypropylene nanocomposite obtains a good liquidity, and meanwhile has a relatively good impact resistance under high-temperature or low-temperature conditions as well as a rigidity. CN102838807A discloses a polypropylene composite material which has a good impact resistance and low-temperature tenacity, and a preparation method thereof. The composite material consists of the following components in percentage by weight: 30-80% of a polypropylene resin, 10-40% of a polyolefin elastomer with low density and low melt index, 1-30% of a reinforcing filling agent, 1-10% of an interface modifier, and 0.1-4% of other additives. All performance indexes of the polypropylene composite material prepared by this method meet or surpass a predetermined requirement, and especially the low-temperature performance is excellent. A failure mode of multiaxial low-temperature impact of the polypropylene composite material (testing according to the ASTMD3763 with an impact speed of 6.6 m/s) is a ductile failure.
The automotive interior parts, such as an instrument board, an auxiliary instrument board, a door panel, an upright, a glove box and the like, mainly use a thermoplastic polypropylenes material and a thermoplastic polyolefins elastomer (TPO). Phenomena of a fracture and a brittle failure may easily occur to a polypropylene material under an effect of an external force in a low-temperature environment. When an airbag blasts, an airbag door fractures partially and a partial fracture flies out, which are caused by an interference of the airbag to a windscreen, a characteristic slot of the instrument board, a characteristic ridge of the instrument board or other structures due to the deployment of the airbag. It would be likely to threaten the safety of the driver and the passengers when an accident happens which causes the blast of the airbag in the automobile.
Therefore, the automotive interior parts are required to ensure an enough tenacity at an extremely low temperature (−30° C.) and no fragment is allowed to fly out to hurt someone. Besides, as the requirements for the interior parts are becoming higher, how to solve the problem of the low-temperature tenacity of the polypropylene material, improve a welding pull-out force between the instrument board and an airbag frame, and meanwhile improve a tenacity of the parts and hence the instrument board as a whole, has become an important research direction of a polypropylene modified material.